On Wed, Oct 14, 2015 at 01:02:22PM +0200, Lars-Peter Clausen wrote: > On 10/14/2015 12:50 PM, Vinod Koul wrote: > > On Thu, Oct 08, 2015 at 04:51:30PM +0200, Lars-Peter Clausen wrote: > >>> The DMA engine API states that > >>> > >>> * device_terminate_all > >>> - Aborts all the pending and ongoing transfers on the channel > >>> - This command should operate synchronously on the channel, > >>> terminating right away all the channels > >>> > >>> I wonder how to interpret "synchronously" here, should terminate_all() wait > >>> for termination to be complete ? In that case it wouldn't be valid to call it > >>> from non-sleepable context. > >> > >> We need to extend the DMAengine API to allow synchronization. The issue is > >> not only the IRQ itself but also the tasklet that can be scheduled from the > >> IRQ. Since we in some cases (e.g. audio underrun) call terminate_all() from > >> within the completion callback that runs in the in the tasklet we can't > >> synchronize to the tasklet in dmaengine_terminate_all(). We need a separate > >> API call to handle this. And then maybe have a helper like > >> dmaengine_terminate_all_sync() that terminates and synchronizes. And in > >> cases where terminate_all is called from a context where it can't > >> synchronize the new API needs to be called separately before freeing the > >> resources. > > > > Right now the terminate_all() is intended for syncronous behaviour which > > prevents it from being invoked in the callback. > > That does not match reality though. Which means the documentation is wrong. > Pretty much all drivers implement a non-synchronous terminate function and > there are users that rely on this. Lets fix that then :) We should have both option IMHO, as I think we have both types of usages... Care to send a patch? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
